The present invention generally relates to superconducting devices. More specifically, the present invention is directed to integrating Josephson amplifiers or Josephson mixers into printed circuit boards.
Superconducting quantum computing is an implementation of a quantum computer in superconducting electronic circuits. Quantum computation studies the application of quantum phenomena for information processing and communication. Various models of quantum computation exist, and the most popular models incorporate the concepts of qubits and quantum gates. A qubit is a generalization of a bit that has two possible states, but can be in a quantum superposition of both states. A quantum gate is a generalization of a logic gate, however the quantum gate describes the transformation that one or more qubits will experience after the gate is applied on them, given their initial state.
The electromagnetic energy associated with the qubit can be stored in so-called Josephson junctions and in the capacitive and inductive elements that are used to form the qubit. In one example, to read out the qubit state, a microwave signal is applied to the microwave readout cavity that couples to the qubit at the cavity frequency. The transmitted (or reflected) microwave signal goes through multiple thermal isolation stages and low-noise amplifiers that are required to block or reduce the noise and improve the signal-to-noise ratio. The microwave signal is measured at room temperature. The amplitude and/or phase of the returned/output microwave signal carry information about the qubit state, such as whether the qubit is at the ground or excited states or at a superposition of the two states. The microwave signal carrying the quantum information about the qubit state is usually weak on the order of a few microwave photons. To measure this weak signal with room temperature electronics, low-noise Josephson amplifiers are usually used as preamplifiers (first amplification stage) at the output of the quantum system to boost the quantum signal and improve the signal to noise ratio of the output chain. In addition to Josephson amplifiers, certain Josephson microwave components that employ Josephson amplifiers or Josephson mixers such as Josephson circulators, Josephson isolators, and Josephson mixers are expected to play a crucial role in scalable quantum processors and quantum communication.
Josephson parametric amplifiers are high-gain, low-noise amplifiers that are used in the readout of qubits and the measurement of quantum systems.
A Josephson ring modulator (JRM) is a nonlinear dispersive element based on Josephson tunnel junctions that can perform three-wave mixing of microwave signals at the quantum limit. The JRM consists of Josephson Junctions (JJs). In order to construct a non-degenerate parametric device that is the Josephson parametric converter (JPC) (which is one example of Josephson parametric amplifiers), which is capable of amplifying and/or mixing microwave signals (without amplification) at the quantum limit, the JRM is coupled to two different microwave resonators.